21287959 has 8 divisors (see below), whose sum is σ = 26540928. Its totient is φ = 16587960.

The previous prime is 21287951. The next prime is 21287993. The reversal of 21287959 is 95978212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21287959 - 2³ = 21287951 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 138157 + ... + 138310.

It is an arithmetic number, because the mean of its divisors is an integer number (3317616).

Almost surely, 2^21287959 is an apocalyptic number.

21287959 is a deficient number, since it is larger than the sum of its proper divisors (5252969).

21287959 is a wasteful number, since it uses less digits than its factorization.

21287959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276485.

The product of its digits is 90720, while the sum is 43.

The square root of 21287959 is about 4613.8876232522. The cubic root of 21287959 is about 277.1477401348.

The spelling of 21287959 in words is "twenty-one million, two hundred eighty-seven thousand, nine hundred fifty-nine".